This invention is related to computer memory systems of a type utilizing small, compact semiconductor memory cards, and particularly to a structure within the cards for densely packing a large number of integrated circuit chips of electrically erasable and programmable read-only-memory (“EEPROM”) to provide a complete memory system.
Currently, standard microcomputer systems use a combination of fixed and removable (floppy) magnetic disk media for long-term, non-volatile memory. Semi-conductor random access memory (“RAM”) without a battery power supply backup is only temporarily used since it is volatile; that is, when power to the computer system is disconnected, contents of the RAM are lost. A small amount of read only memory (“ROM”) is also included for permanent storage of certain computer system parameters that do not change.
There is currently underway an effort to develop non-volatile flash EEPROM memory systems to replace either of the existing fixed or floppy magnetic disk systems, or both. It is now becoming possible to form a megabyte or more of flash EEPROM on a single semiconductor integrated circuit chip. As a result, several megabytes of memory can be formed in a very small package.
Indeed, an industry “PC Card Standard”, release 1.0, dated August 1990, of the Personal Computer Memory Card International Association (PCMCIA) sets mechanical and electrical interface standards for a memory card that is not much larger than an ordinary credit card. Although some physical dimension variations are permitted within the scope of this standard, it is less than 6.0 mm in overall outside thickness, less than 5.5 cm in width, and less than 9.0 cm in length. A female type of pin connector is provided across one of the narrow ends of the card structure. Such PC cards have been commercially implemented primarily with static random-access-memory (“SRAM”) and ROM.
It is a principal object of the present invention to provide a structure for packaging a large number of flash EEPROM integrated circuit chips within such a PC card or other standard structure, thereby providing a large memory capacity in an individual card or other industry standard physical configuration.
It is another object of the present invention to provide a complete flash EEPROM system within such an individual card or other standard configuration that emulates a floppy or hard disk system.
It is a further object of the present invention to provide such a PC card structure that is easy to fabricate and test during assembly.
It is yet another object of the present invention to provide an improved computer memory system that utilizes one or more PC cards containing EEPROM integrated circuit chips.